nrf52832 - TWIM vs TWI - Transfer with long FIFOs

RE: nrf52832 - TWIM vs TWI - Transfer with long FIFOs

akshaymishra — Fri, 21 May 2021 07:53:18 GMT

blocking mode nailed it !

RE: nrf52832 - TWIM vs TWI - Transfer with long FIFOs

Kenneth — Thu, 20 May 2021 14:40:44 GMT

Any difference if you run this in blocking mode instead?

https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.0.2/hardware_driver_twi.html#hardware_driver_twi_basic

RE: nrf52832 - TWIM vs TWI - Transfer with long FIFOs

akshaymishra — Thu, 20 May 2021 12:30:00 GMT

I am, as yet, verifying my twi attempts with less than 255 bytes which does not seem to succeed. Have not attempted >255 bytes - not knowing what else it'll throw at me.

RE: nrf52832 - TWIM vs TWI - Transfer with long FIFOs

Kenneth — Thu, 20 May 2021 12:22:26 GMT

The TWIM on nRF52832 only support 255bytes (8-bit), ref MAXCNT register:
https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/twim.html#register.RXD.MAXCNT

So if you set a value larger than 255bytes, it likely will likely mask bits that are >8-bit, thereby only a few bytes are read.

The actual MAXCNT are different between nRF52 variants, see here:
https://devzone.nordicsemi.com/f/nordic-q-a/50513/twi-maximum-data-transfer-size-in-nrf52832/202150#202150

However the twi driver should not have such limitation, since each byte will then be handled in interrupt mode. Though the twi driver was made back in the days when 8-bit was what was sufficient, so maybe there is something leftover 8-bit that prevent this to work as intended.

"When using nrfx_twi_rx -- the clock is visible for the duration but the data is not captured."

Does it works when <255bytes?

I could find this case that maybe is related:
https://devzone.nordicsemi.com/f/nordic-q-a/33996/twi-sending-wrong-data---sdk15

Maybe check the buffers are static.

Kenneth

RE: nrf52832 - TWIM vs TWI - Transfer with long FIFOs

akshaymishra — Thu, 20 May 2021 09:52:06 GMT

The slave is transmitted transmitting correctly. With twim reads the data is latched correct but with twi reads the only first few bytes (8-12) bytes get captured. the SDA line shows valid data.

Edit: grammar

RE: nrf52832 - TWIM vs TWI - Transfer with long FIFOs

awneil — Thu, 20 May 2021 09:25:13 GMT

[quote userid="91089" url="~/f/nordic-q-a/75373/nrf52832---twim-vs-twi---transfer-with-long-fifos/310644#310644"]the data is not captured[/quote]

not sure what you mean by that?

the Slave is transmitting correctly on SDA, but your software is not seeing that data?
there is no activity on SDA?
other ... ?

RE: nrf52832 - TWIM vs TWI - Transfer with long FIFOs

akshaymishra — Thu, 20 May 2021 08:58:09 GMT

When using nrfx_twim_rx -- I can read upto 255 bytes without any issue.

When using nrfx_twi_rx -- the clock is visible for the duration but the data is not captured. No change in hardware/ settings.

I am attempting the nrfx_twi_rx since I assume I will be able to eventually read >255 bytes in 1-trasaction.

thanks,

RE: nrf52832 - TWIM vs TWI - Transfer with long FIFOs

awneil — Thu, 20 May 2021 07:55:15 GMT

have you used a scope or analyser to check what's happening on the wires?